The present invention relates to vehicle drive belts or tracks of the type intended for installation across a pair of rubber wheels of a vehicle and comprising track links which extend across the shoulders of the wheels, and more particularly to such track links having cylindrical holes in the longitudinal direction of the tracks for receiving respective longitudinal connecting units which connect the track links together.
The expression "drive track" is used herein to denote a track-like device intended to be placed across a pair of wheels of a vehicle so as to achieve an arrangement similar to caterpillers of crawling treads, but wherein the wheels are rubber wheels. Arrangements of this type have arroused increasing interest in recent years since requirements demand a lower surface pressure per unit area in many cases than can practically be achieved by means of a pair of drive wheels. Driving more than one pair of wheels (i.e., four-wheel drive) by means of a universal joint entails extra costs, as do solutions involving ordinary caterpillars. It has proved economic in this context to place some type of belt or track across two or more wheels. The simplest such version consists of a track of interconnected steel links which run across two wheels. The use of a steel track of this type involves, however, the disadvantage of comparatively large stresses on bearings, etc., since the track links are not flexible and are not sprung. Thus, all of the spring action must be absorbed by the rubber wheels and their bearings. Against this background, it has been deciced to make the track's individual track links of urethane rubber since this material has satisfactory strength properties and satisfactory resistance to abrasion, as well as satisfactory elasticity compared with, for example, steel links.
The known track links of urethane rubber have been connected by means of chain links which engage projecting lugs or teeth. The projecting lugs must be reinforced and doing so requires an amount of material which is by no means negligible. The lugs must be strong not only to transmit any tensile forces which may occur but also to withstand the major forces which arise when, for example, the center of the track links is pressed up--when crossing for example, stones and stumps--to such an extent that the track link changes or attempts to change its curvature. As can readily be understood, this also means that the link system connecting the individual track links together must be strong. The strength requirements result in comparatively large dimensions for the chian links and, above all, for the lugs or teeth on the track links, and space problems can arise in certain machines, particularly those which are small in size. In this context it should also be noted that an increase in width of the track does not, unfortunately, benefit the contact surface but merely entails a loss of space. As a result of the spatial disadvantage mentioned above and of the considerable quantity of material consumed, the competitive situation for track links made of urethane rubber has suffered, despite the superiority of this material in other respects.
The object of the present invention is to provide a drive track in which the material consumption is minimized, in which the dimensions of the connecting units have been decreased so that drives of this type can be made economically justifiable even in small applications such as, for example, the drive track for mini-loaders. The invention is not, of course, limited to small applications but can also be used to advantage for large machines.